A material that is melted and reformed as part of a joint between two work pieces during a welding or brazing process is commonly called a consumable insert. Consumable inserts may take many forms depending upon geometry of the joint and the materials being joined. Consumable inserts having a generally thin, flat shape are commonly called ribbon inserts because their shape suggests the shape of a ribbon. If the thickness of the material is sufficiently thin, the ribbon insert may be referred to as a foil. Ribbon inserts are limited to ductile materials, since the cold working necessary to form the material into the ribbon shape can only be accomplished with a ductile material. Consumable non-ductile materials are typically introduced into a metals joining process in particulate form. Powder feed devices used to store, handle and distribute such non-ductile materials typically require that the particulate material to be in the shape of spheres in order to facilitate the smooth movement of the particles through the device mechanism.
A process that has been used successfully for repair and material addition to superalloy components is known by several different names: diffusion bonding; diffusion brazing; liquid phase diffusion sintering; and transient liquid phase bonding. These names generally refer to a process wherein a consumable material is melted at a temperature that is less than the liquidous temperature of a work piece and then is caused to solidify to become integral with the work piece. The consumable material may typically include a melting point depressant such as boron or silicon to ensure that the consumable material will melt at a temperature that does not risk melting of the work piece. The work piece and consumable material are held at an elevated temperature for a sufficient interval to promote diffusion of the melting point depressant into the work piece material. As the melting point depressant diffuses, the melting point of the remaining consumable material will increase and the liquid material will solidify to form the desired joint or coating. Consumable inserts used for the transient liquid phase bonding of superalloy materials may be formed of nickel, with the boron melting point depressant having been diffused into the nickel substrate.